1192results about "Electric/magnetic contours/curvatures measurements" patented technology

A fingerprint-reading system comprises a fingerprint sensor having an active surface sensitive to the pressure and temperature of a finger. The surface area of this sensor is far smaller than the surface area of the fingerprint to be read. The reading is done when the sensor and the finger are in contact and in a relative motion of sliding of the sensor and the finger with respect to each other. The system has means to reconstitute a complete image of the fingerprint from the partial images given by the sensor during this motion. Application inter alia to devices for the authentication of individuals.

The invention relates to a measurement method for determining the position and the orientation of a moving assembly in a base frame of reference. According to the invention, the method comprises the steps of: taking an image of an optical reference mark associated with the moving assembly by means of a first camera having a focal axis lying in a direction that is known in the base frame of reference; taking an image of an optical reference mark associated with the first camera by means of a second camera associated with the moving assembly; measuring the distance between a point associated with the first camera and a point associated with the second camera by using self-contained measurement means that are independent of said first and second cameras; and computing the position and the orientation of the moving assembly in the base frame of reference on the basis of the images taken and of the measured distance.

A piezoelectric thin film sensor array is used to scan and capture biometric data, for example, a fingerprint image. In one embodiment, a multi-layer structure includes a PVDF layer in between two conductor grids arranged orthogonally to one another. Urethane can be added to one side where a finger is placed. A foam substrate can be used as a support. In one feature, the PVDF, and grids can be peeled off like a label for easy replacement. Multiplexers are switched to scan the sensor. A single pixel or a group of pixels can be detected and output to an image memory. The presence of a fingerprint ridge is detected by virtue of a ring-down oscillation that arises from reflection when an electric field is applied to the piezoelectric thin film sensor array at a pixel in contact with the fingerprint ridge. For example, such a ring-down value associated with a fingerprint ridge can be detected at about 150 ns. (or 5 cycles at 30 MHZ). Other reflections indicative of additional biometrics (e.g. from tissue, blood, bone, fingernail, etc.) can also be detected. A Doppler effect due to reflections from circulating blood can also be detected. Such a Doppler effect can provide further information about direction and speed of blood circulation. An instantaneous pyroelectric effect can also be detected to indicate a live finger presence.

A fingerprint area and a barycentric position of the area are obtained for a current sensor image, and an area near the barycentric position is divided into a plurality of small blocks. An image area that agrees with a fingerprint image is searched for, for each of the small blocks with respect to the fingerprint area in a previous sensor image. A candidate vector is obtained from a deviation between the position of the small block in the current sensor image and the position of the image area in the previous sensor image corresponding to the small block. A candidate vector with the highest matching degree between the fingerprint images in the current and previous sensor images is selected from the candidate vectors to obtain a detected vector, and the detected vector is corrected to exclude an influence of erroneous detection and to control a movement of a pointer.